Try this one, http://www.rapidunlockers.com/
I have unlocked My phone there. Very fast service and cheap, now i can update to any version without having to worry that my phone will be locked ever again.

For those users that are planning to Jailbreak on iOS 6.1.2 then I recommend adding this Cydia Source into Cydia after you jailbreak so you don't have to manually input all the Cydia Sources manually. This will automatically add all the best Cydia Sources and give you access to all the best Cydia Tweaks, Themes and Apps for FREE with just a push of a button. Follow the steps below.
1. Open Cydia
2. Tap Sources
3. Tap Edit
4. Tap Add
5. Type this url in the box (cydiasource,n e t) without the spaces and switch coma for a dot in the url.
6. Tap "Add Source"
7. Install the package labelled "All Sources".
This will give you all the best Cydia Sources to have access to all the best Tweaks, Apps and Themes for FREE.

I have iphone4 ios6.0.1 I have successfully installed cydia. However, it is frustrating as I am unable to unlock it using SAM/ultrosn0w/fixer etc.
Tried all the above but the phone refuses to work with a sim from another network in another country
Very frustrated.
All methods to unlock the phone to work on a network in India has failed as the phone was bought in US
Any help on where I am going wrong or instructions you can provide will be highly appreciated
thanks
espee